Spark-plug for internal-combustion engines.



J. E. SHELBY.

SPARK PLUG FOR INTERNAL COMBUSTION ENGINES.

APPLICATION FILED NOV. 26. 1909.

Patented Dec. 13,1910.

sTATEs PATENT OFFICE.

JAMESE. SEELEY, OFIrOS ANGELES, CALIFORNIA, ASSIGNOR TO HIGH FREQUENCY IGNITION COIL COMPANY, OF LOS ANGELES, CALIFOKN IA, A CORPORATION OF CALI- FORNIA.

SPARK-PLUG FOR I-NTERNALGOMBUSTLEON ENGINES.

Patented Dec. 13, 1910;

Application filed November 26, 1909. Serial No. 530,011.

To all whom 'it may concern:

Be it known that I, JAMES E. SEELEY, a citizen of the United States, residing at Los Angeles, inthecounty of Los Angeles and State of California, have invented a new and.useful Spark-Plug for Internal-Com bustion Engines, of which the following is a. specification.

This invention relates to a spark plugfor igniting the explosive charge in internal combustion engines and the main object of the invention is to minimize the loss in the spark plug due to electro-static induction therein. 7

In spark plugs as usually constructed the inner and outer conducting members of the spark plug are, in general, insulated from one another by solid materials presenting a relatively high coeflicient of clectro-static induction, or of specific inductive capacity. According to the present invention there is interposed or provided in the insulation between such inducting parts a space containin material of low specific inductive capacity, namely, .an air space.

A further object of the invention is to provide improvedelectrode means for the spark plug. s

In the accompanying drawings illustrating the invention: Figure 1 is a vertical section of the'spark plug. Fig. 2 is a side elevation thereof. Fig. 3 is a horizontal section on the line w -w in Fig. 1.

1 designates a plug body screw-threaded at 2 to screw into the usual tapped opening in the cylinder of an internal combustion engine. Thebody 1 is bored centrally to receive the insulating body or member 3, said member 3' having'an annular projection or flange 4 which is clamped between a shoulder 5 in the bore of the. plug body 1 and a shoulder'formed by the inner end of the screw plug or bushing 6 screwing into the upper end of the bore in the body 1, suitable washers 12 being interposed between the said shoulders and the flange 1 to give an even clamping action on said flange.

The outer electrode .7 is attached to the lower end of the plug body 1 and the inner electrode 8 is attached to an electrode bar or rod 9 supported by the insulating member 3, the upper port-ion or shank 9 of this rod being clamped to the member 3 by a nut 10 screwing on said shank and drawing a shoulder 11 of said shank against a shoulder of the member 3. A ferrule 13 may be provided encircling the upper'end of the insu-1 lating'member3. Electrode shank 9 may be provided with the usual connecting means or binding nut 16.

Insulating member 3 is tapered at each end so as to leave an air space between the formed in the axial perforation or bore 17 v lar insulating material. Such material is of relatively high specific inductive capacity as compared with air and in order to minimize the loss due to electro -static induction through the insulating body, the said member 3 is recessed or formed with a central space or chamber as shown at 17 said chamber, for example, being central or axial and directly around the bar 9, said bar passing axially within said recess; said recess is preferably tubular and coaxial with the member 3 and is preferably of such length that it extends between the inner electrode conductor 8 and the surrounding metal parts, namely, body 1 and bushing 6, so that these conducting parts is exerted through the relatively low di-electric constant or speelectro-static induction taking place between this intervening air space and on account of cific inductive capacity of the air as com- 1 flange 4 to a point farther in than said flange so as to present an air gap within said flange and thereby protect against loss by static induction at that part of the length of the plug where the external or surrounding air gap above referred to is not present on account'of the presence of the flange for sup porting the insulating member in place. In

order to prevent accumulation of solid matemember from a point farther out than said rial Within the tubular recess 17 the latter is preferably closed at its lower end by a plug or bushing 19, said plug or bushing being preferably below the inductive sphere of 1nfluence of the outer conducting member. The insulating supporting member 3 preferably tapers from the flange 4 upwardly and downwardly, so that on account of the air spaces thus provided around said end rtions the electro-static induction is mainly concentrated in the vicinity of the flange 4, and it is at this portion of the plug that the efiectof the air space 17 in reducing the electro-static induction is especially effective.

The inner electrode 8 is referably formed as an inverted cone screwing into the lower end of bar 9, and the outer electrode 7 is preferably bent inwardly and upwardly so as to extend in proximity to the conical surface of electrode 8. This construction enables a new or different portion of the inner electrode to be presented for sparking, when necessary, by simply rotating the electrode in its support.

the outer end thereof and provided with an interior cham er surrounding said inner conducting member and forming an air gap between said inner conducting member and the aforesaid flange portion so as to present an air gap at that ortion of the length of the spark plug at w ichthere is no external air gap surrounding the insulating member.

2, A spark plug comprising an outer supporting and conducting member provided with an electrode, an inner conducting member rovided with an electrode and an intermedlate insulating member having a flan portion in contact with and secured to sald outer conducting and supportin member andhaving a portion at each en which is tapered so as to be out of contact with said outer conducting member so as to form an air gap surrounding the insulating member at each end portion thereof and sald insulating member supporting said inner conducting member at the outer end thereof and provided with an interior chamber surrounding said inner conducting member and forming an air gap between said inner conducting member and the aforesaid flange portion so as to present an air gap at that portion of thelength of the spark plug at which there is no external air gap surrounding the insulating member.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 11th day of August 1909.

JAMES E. SEELEY. 

